This invention pertains to an electronically-controlled precision drive for moving a film web; in both longitudinal and transverse directions.
Such a drive is frequently used for successively positioning unexposed photographic film for exposing the same in a microfiche camera having a stationary lens.
One such camera is that of Burton et al, U.S. Pat. No. 3,601,487, a camera that has been well-known in the art for several years. A different structure and mode of electronic control of the present invention achieves greater accuracy.
In this U.S. Pat. No. 3,601,487 the longitudinal drive for the film is accomplished by one stepper motor simultaneously driving two spaced rollers 21 and 22. The transverse (orthogonal) drive is accomplished by a cable system that acts upon a carriage and employs one rotary encoder at one point along the cable. A servo-motor 8 drives the cable under the logic control of the rotary encoder.
Another camera is that of Roberts et al, U.S. Pat. No. 3,767,302.
Again, the longitudinal drive for the film is accomplished by one stepper motor; which, however, drives only roller 18. At the other (top) end of the exposure area there are merely guide rollers, free rolling.
The transverse drive is accomplished by a rack upon a carriage, with a pinion on a stationary motor engaging the rack. The carriage also carries linear format control means; i.e., an opaque strip having gross apertures related to the spacing between individual frames of the fiche and the number of such frames to be accomodated. (This gross type of encoder is the same type as the rotary encoder utilized by Burton, U.S. Pat. No. 3,601,487.)